Precision longitudinal movement transmission cable

ABSTRACT

The precision longitudinal movement transmission cable, includes a tubular casing (T) and a cylindrical central core (N) contained in the tubular casing (T) and having a plurality of radial projections (5) extending longitudinally over the entire core length and being provided with a central metal cable (4) for axial reinforcement. The longitudinally extending radial projections define a plurality of longitudinally extending equidistant channel-like grooves (6) and the cylindrical central core (N) fits in the tubular casing (T) so that it can slide and rotate. The transmission cable is also provided with a retaining device in each of the channel-like grooves (6) providing partitioning walls defining a plurality of compartments (9) of equal compartment length arranged in longitudinal succession along each of the channel-like grooves (6); and a plurality of balls(10), each of the balls being located in one of the compartments (9) of the channel-like grooves (6) and being dimensioned so that the balls can move snugly along an inner surface of the tubular casing (T) and in the channel-like groove (6) along the entire compartment length of the compartment (9) when the central core (N) is moved longitudinally. The retaining device can be a metal wire (7) uniformly helically coiled around the central core (N).

BACKGROUND OF THE INVENTION

The present invention relates to movement transmission cables and, moreparticularly, to a precision longitudinal movement transmission cablewhich is particularly applicable as a connecting member between thecontrol lever and the automatic transmission of motor vehicles.

It is well known that in motor vehicles fitted with an automatictransmission as original equipment the connection between the gear levermounted in the vehicle interior and the automatic transmission iseffected by longitudinal movement transmission cable, unlike vehiclesprovided with a manual transmission as original equipment in which theconnection between the gear lever and the transmission is effectedgenerally by a set of articulated rigid metal rods.

The purpose of the longitudinal movement transmission cables is totransfer to the automatic transmission the movement that the driverapplies to the gear lever. The flexible nature of these transmissioncables is important for their use as a connecting member between thegear lever and automatic transmission in view of the relative positionsof both, generally involving an undulating path for the connection.

Generally speaking, these longitudinal movement transmission cables arebasically formed by a longitudinal central band or core housed in acasing adapted to the operational conditions of the cable. The centralcore may slide relative to the casing with the aid of bearings.

Among the known longitudinal movement transmission cables incorporatingthe novel features characterizing them which have been described inessence in the foregoing paragraphs, the following may be cited: Frenchpatent 70.39958, describing a longitudinal movement transmission cablewherein the central core consists of a continuous prismatic bandlongitudinally movable between two opposed rows of running members whichrespectively bear against a guide channel attached to the cable casing;French patent 73.15135, describes a longitudinal movement transmissioncable comprising a longitudinally movable central prismatic core, two ofthe sides whereof bear on continuous bands provided with running memberswhich bear against the inner surface of the cable casing; and Spanishpatent 308,365, which describes a longitudinal movement transmissioncable having a cylindrical central core longitudinally movable onrunning members housed in a plurality of interconnected supportsconcentric to the main core.

Generally speaking, the known embodiments of longitudinal movementtransmission cables suffer from the fact that they comprise a largenumber of components parts are complex to make and assemble. This istheir main drawback. On the one hand, all of this makes production andassembly costs comparatively more expensive and, on the other hand,causes comparatively frequent breakdowns and/or faulty operation of thecable.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a longitudinalmovement transmission cable having a smaller number of components whichare easier to make and assemble, than the known transmission cables, aswell as a high degree of operational reliability.

The precision longitudinal movement transmission cable of the inventioncomprises a tubular casing of a structure and composition appropriatefor each particular application and an essentially cylindrical centralcore of the same length as the tubular casing containing it and which isprovided with a central axial reinforcement constituted by a metalcable. The central core is formed with a sufficient number of radialprojections, at least three and preferably five, extendinglongitudinally without a break over the whole length of the centralcore, the radial projections defining corresponding equidistantchannel-like grooves, the theoretical outside diameter given by the freeends of the radial extensions being smaller than the inside diameter ofthe tubular casing, so that the central core may slide and rotate aboutits own axis inside the tubular casing, wherein in each of thechannel-like grooves retaining means which in the style of partitionwalls define a plurality of compartments of equal length in longitudinalalignment along the grooves, wherein in each of the compartments of thechannel-like grooves a ball which, when the central core is housed inthe tubular casing, may snugly roll along the inner surface of thetubular casing and on the surface of the channel-like groove of thecentral core containing it, along the whole length of the compartmentwhen the central core is moved longitudinally in any direction.

In a preferred embodiment of the precision longitudinal movementtransmission cable of the invention the retaining means on the centralcore consists of a metal wire uniformly helically wound about the wholelength of the central core. This winding is housed in grooves which,angularly mating with the helically wound metal wire winding, are formedon the free ends of the radial projections of the central core, suchthat the metal wire defines in the channel-like grooves longitudinallyadjacent compartments of like lengths.

The small number of components of the precision longitudinal movementtransmission cable of the invention in comparison with the knownembodiments, as well as the simplicity of manufacture and assembly ofthese components are fundamental factors in the reduction of productioncosts.

The cable of the invention also offers, because of its characteristicstructure, a very high reliability and accuracy of operation, as well asa minimum wear of the constituent parts thereof which, under normalconditions of use, ensures a very high number of operations or movementsof the central core relative to the casing in its reciprocatingmovements.

The tubular casing is, under conditions of use, attached at therespective ends thereof by corresponding connection terminals to theautomatic transmission change lever and to the correspondingtransmission mechanism.

The maximum length over which the central core may be longitudinallymoved relative to the tubular casing of the precision longitudinalmovement transmission cable of the invention is defined precisely by theretaining means of the central core and, in particular, by the length ofthe compartments the retaining means define in each of the channel-likegrooves of the central core.

As described above, each ball housed in its corresponding compartment ofthe central core may roll simultaneously along the inner surface of thecorresponding channel-like groove of the central core to the extentdefined by the length of the compartments when a force sufficient tomove the central core relative to the casing is applied to one of theends thereof. When the ball reaches the retaining means defining thecompartment in either of the two possible directions of movement of thecentral core and the force is held applied to one of the ends thereof,the ball may not continue rolling and could only continue moving bysliding and rubbing against the surfaces. By extension, this frictionoccurs all along the cable at the plurality of balls housed in theirrespective compartments defining the retaining means in the central coreof the cable of the invention which means that, from the time whenmovement of the central core relative to the casing is such that theballs housed in the compartments of the central core reach the end oftheir rolling path in the compartments they then oppose the furthermovement of the central core with such a high resistance that it isnecessary to use a very high force to continue moving the central core.

In the light of the foregoing, the precision longitudinal movementtransmission cable of the invention may, on the one hand, transmit thelongitudinal movement under the conditions described above and, on theother hand, it may limit such longitudinal movement, adapting it to theneeds of each particular application, thereby preventing the mechanismsand/or devices receiving such longitudinal movement or, which is thesame, receiving the traction and compression forces, from being exposedto mechanical overloads which frequently cause breakdowns and/ormisfunctioning of the mechanisms and/or devices.

BRIEF DESCRIPTION OF THE DRAWINGS

The objects, features and advantages of the present invention will nowbe illustrated in more detail by the following detailed description,reference being made to the accompanying drawing in which:

FIG. 1 is a longitudinal cross-sectional view of a preferred embodimentof the precision longitudinal movement transmission cable according tothe invention; and

FIG. 2 is a transverse cross-sectional view of the transmission cable ofFIG. 1 taken along the section line II--II of FIG. 1.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The embodiment of the precision longitudinal movement transmission cableof the invention comprises a central core N and the tubular casing Tcontaining it.

In this embodiment, the precision longitudinal movement of thetransmission cable of the invention is, as said above, for connectingthe gear lever arranged in the passenger compartment of the vehicle withthe automatic transmission. To this end, the transmission cable isprovided at both ends with corresponding connection terminals which, forgreater clarity, have not been shown in the drawing sheet.

FIGS. 1 and 2 show that the tubular casing T comprises, in thisembodiment of the precision longitudinal movement transmission cable ofthe invention, the outer protective sheath 1, a plurality of reinforcingcables 2 and a inner running sheath 3.

The outer protective sheath 1 and the inner running sheath 3 arepreferably made of plastics materials of properties appropriate fortheir respective purposes.

The reinforcing cables 2, as shown in detail in FIG. 2, are arrangedbetween the outer protective sheath 1 and the inner running sheath 3,being concentrically wound around the inner sheath 3 and extending allalong the tubular casing T. The cables 2 are metallic and act asstructural reinforcement for the casing T.

All the foregoing concerning the tubular casing T is well known and thetubular casing T may have any other composition and structureappropriate for the needs of each particular application of theprecision longitudinal movement transmission cable of the invention.

FIG. 1 shows how the central core N is coextensive with the tubularcasing T. The central core N is provided with a central axialreinforcement comprising the metal cable 4 coextensive with the centralcore N.

FIG. 2 shows how the central core N is essentially cylindrical and isformed with the identical equidistant radial projections 5 of which, inthis embodiment, there are five. The number of radial projections 5 mayvary depending on the needs of each particular application. It should benoted that the minimum number of radial projections 5 with whichadequate working of the precision longitudinal movement transmissioncable of the invention is obtained is three.

The radial projections 5 extend continuously along the central core Nand have an essentially trapezial section, with the shorter ends thereofarranged at the free ends of radial projections, such as shown in FIG.2.

FIG. 2 shows how the radial projections 5 are dimensioned in such a wayas to define the curved profile channel-like grooves 6 which, like theradial projections 5, are coextensive in this embodiment with thecentral core N as shown in FIG. 1. Logically, the number of channel-likegrooves 6 is the same as the number of radial projections 5.

The free ends of the radial projections 5 define, as shown in FIG. 2,the theoretical outside diameter of the central core N. This diameter,which is smaller than the inside diameter of the running sheath 3 of thetubular casing allows the central core N to slide longitudinally androtate about itself snugly relative to the tubular casing T.

FIGS. 1 and 2 show how the metal wire 7 is uniformly helically woundaround the central core N. This wire is positionally fixed relative tothe central core N by the action of the transverse grooves 8 which,forming the same angle relative to the center axis of the central core Nas defined by the helical winding of the metal wire 7, are formed in thefree ends of the radial projections 5 of the central core N.

The transverse grooves 8 are dimensioned in such a way as snugly tocontain the portions of the metal wire 7 crossing therethrough. In thisway, the metal wire 7 does not project outwardly relative to the centralcore N, as shown in FIGS. 1 and 2.

FIG. 1 shows how the metal wire 7 helically wound around the centralcore N, defines in the channel-like grooves 6, the longitudinalcompartments 9 which are of equal length and transversely adjacent alongthe central core N. These compartments 9 are thus longitudinally boundedby the portions of metal wire 7 angularly arranged across them andtransversely by the radial projections 5 of the central core N.

In each of the compartments 9, as shown in FIG. 1, there is housed apreferably metallic, and to be more precise, a steel ball 10, thediameter of which allows the ball 10 simultaneously to roll along theinner surface of the running sheath 3 of the tubular casing T and rollover the surface of the channel-like groove 6 of the central core N whenthe central core N is in the tubular casing T and is movedlongitudinally relative thereto.

When the precision longitudinal movement transmission cable of theinvention is fixed at both ends thereof, by corresponding connectionterminals, respectively to the gear lever and to the automatictransmission, it works as follows:

FIG. 1 shows the position occupied by the central core N relative to thetubular casing T when no force is being applied to the central core N.Under these conditions, the balls 10, housed in their respectivecompartments 9, occupy the position shown in FIG. 1, i.e. touching themetal wire 7 which, as said above, longitudinally bounds the ends ofeach of the compartments 9, the balls 10 being retained in this positionby the snug fit with which they are housed in their respectivecompartments 9, under normal conditions of use of the cable of theinvention;

when a sufficient force is applied to the end A of the central core N inthe direction S in FIG. 1, the central core N is moved longitudinally ofthe tubular casing T in the direction S bearing on the balls 10 whichroll simultaneously on the inner surface of the running sheath 3 of thetubular casing T and on the inner surface of the channel-like grooves 6of the central core N whereby the longitudinal movement of the centralcore N relative to the tubular casing T is sufficiently approximate totwice the longitudinal movement of the balls 10;

when the balls 10 reach the opposite end of their respectivecompartments 9, if the force is maintained on the end A of the centralcore N in the direction marked as S, the balls 10 are prevented fromcontinuing to roll by the metal wire 7, so that they may only continuemoving by sliding and rubbing against the surfaces, i.e. the innersurface of the running sheath 3 and the surface of the channel-likegrooves 6;

therefore, the joint friction produced under the conditions describedimmediately above by the plurality of balls 10 housed in theirrespective compartments 9 of the central core N prevents the centralcore N from continuing to move longitudinally under normal conditions ofuse, and in order to obtain continued longitudinal movement of thecentral core N, it is necessary to apply a much greater force thaninitially applied to the end A thereof. In this way, as said above, thejoint action of the metal wire 7 and of the balls 10 effectively markthe limits of the maximum distance over which the central core N may bemoved longitudinally relative to the tubular casing T;

the return of the central core N to the preciously described initialposition requires a force of sufficient magnitude to be applied in theopposite direction, marked D in FIG. 1, to S to the end A whereby thecentral core N will be moved in direction D until the balls 10 reach theposition shown in FIG. 1 where the process described in the foregoingparagraphs can be repeated.

While the invention has been illustrated and described as embodied in aprecision longitudinal movement transmission cable, it is not intendedto be limited to the details shown, since various modifications andstructural changes may be made without departing in any way from thespirit of the present invention.

Without further analysis, the foregoing will so fully reveal the gist ofthe present invention that others can, by applying current knowledge,readily adapt it for various applications without omitting featuresthat, from the standpoint of prior art, fairly constitute essentialcharacteristics of the generic or specific aspects of this invention.

What is claimed as new and desired to be protected by Letters Patent isset forth in the appended claims.

We claim:
 1. A precision longitudinal movement transmission cable fortransmitting a longitudinal movement, comprising: a tubular casing (T)extending longitudinally and having a casing length; a cylindricalcentral core (N) having a core length and being contained in the tubularcasing (T), said casing length being substantially equal to said corelength, said central core (N) having a plurality of longitudinallyextending radial projections (5) extending longitudinally over the corelength and being provided with a central metal cable (4) for axialreinforcement, said radial projections defining a plurality oflongitudinally extending equidistant channel-like grooves (6) in thecentral core (N) and said radial projections (5) having free endsdefining an outside diameter of the cylindrical central core (N) relatedto an inside diameter of the tubular casing (T) such that thecylindrical central core (N) slides and rotates inside said tubularcasing (T); retaining means in each of said channel-like grooves (6)acting as partition walls defining a plurality of compartments (9) ofequal compartment length and in longitudinal succession along each ofsaid channel-like grooves (6); and a plurality of balls (10), each ofsaid balls being located in one of said compartments (9) of thechannel-like grooves (6) and being dimensions so that said balls movesnugly along an inner surface of the tubular casing (T) and in thechannel-like groove (6) along the entire compartment length of saidcompartment (9) when the central core (N) is moved longitudinally, theretaining means on the central core (n) consisting of a metal wire (7)uniformly helical bound about the entire core length of said centralcore (n), said metal wire being at least partly accommodated in aplurality of grooves (8) provided in the central core (N) in thevicinity of free ends of the radial projections (5) thereof so that themetal wire (7) defined equal-length longitudinally adjacent ones of thecompartments (9) in the channel-like grooves (6).
 2. A precisionlongitudinal movement transmission cable according to claim 1, whereinthe number of radial projections is three.
 3. A precision longitudinalmovement transmission cable according to claim 1, wherein the number ofradial projections is five.
 4. A precision longitudinal movementtransmission cable for transmitting a longitudinal movement, comprising:a tubular casing (T) extending longitudinally and having a casinglength; a cylindrical central core (N) having a core length and beingcontained in the tubular casing (T), said casing length beingsubstantially equal to said core length, said central core (N) having aplurality of longitudinally extending radial projections (5) extendinglongitudinally over the core length and being provided with a centralmetal cable (4) for axial reinforcement, said radial projectionsdefining a plurality of longitudinally extending equidistantchannel-like groove (6) in the central core (N) and said radialprojections (5) having free ends defining an outside diameter of thecylindrical central core (N) related to an inside diameter of thetubular casing (T) such that the cylindrical central core (N) slides androtates inside said tubular casing (T); retaining means in each of saidchannel-like grooves (6) acting as partition walls defining a pluralityof compartments (9) of equal compartment length and in longitudinalsuccession along each of said channel-like grooves (6); and a pluralityof balls (10), each of said balls being located in one of saidcompartments (9) of the channel-like grooves (6) and being dimensions sothat said balls move snugly along an inner surface of the tubular casing(T) and in the channel-like groove (6) along the entire compartmentlength of said compartment (9) when the central core (N) is movedlongitudinally, the tubular casing comprising a plastic outer protectivesheath (1), a plurality of reinforcing cables (2) and an inner plasticrunning sheath (3), said reinforcing cables (2) being located betweensaid plastic outer protective sheath (1) and said inner plastic outerprotective sheath (3).